1974 power brakes... which plunger to use?

[74bigblock]

The new brake booster came with two plungers a short one and a long one. I have a new dual master cylinder to go with it... any idea which plunger is correct? I think it's the long one, but I can't get the old units separated to compare.

Thanks!

Dave

 

[JohnZ]

The "long" booster pushrod on the left (4") is used with master cylinders with the "deep" (1-5/8") hole in the rear piston; the "short" booster pushrod on the right (2-5/8") is used with master cylinders with the "shallow" (3/8") hole in the rear piston. Note the O-ring on the pushrod - it's to seal vacuum; the pushrods simply pull straight out of the booster - there's no retainer holding them in.